There shouldn't be anything that persists in regards to audio, we're not altering system volumes or anything like that.
Additionally, if something has gone wrong in the driver, a restart would typically clear it.
The one thing to check, is the various volume controls in windows itself, there are quite a few, and it's easy to turn down the volume in one place, while it's up in others.
Other then that, I've had some odd cases with usb headphones that go really quiet. It's not related to any specific application and a driver re-install is the fix. (This happened to me on a set of g-35 headphones for instance)